09.08.08: Epithelium

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CellsandTissuesSequenceMedicalHistology

Epithelium

Fall,2008

[Fr.Tissu,woven;L.texo,toweave]

Atissueisanorganizedaggregationofcellsorgroupsofcellsthatfunctioninacoordinatedmannertoperformoneormorespecificfunctions.Tissuescombinetoformlargerfunctionalunits,calledORGANS.Thus,thetissuesarethebasicfunctionalunitsresponsibleformaintainingbodyfunctions.

Tissues

BASICTISSUES

EpitheliumConnectivetissue

MuscleNervoustissue

Epitheliumisacohesivesheetofcellsthat:1.Coverstheexternalsurfaceandlinestheinternalsurfaceofthebody.–  Protection(bywithstandingwearandtear,fromhydrationanddehydration)

–  Transport(i.e.O2andC02)–  SelectiveAbsorption:(Controlthemovementofsubstancesbetweentheoutsideenvironmentandtheinternalcompartmentsinthebody.)

–  Secretion(secretorycells)

2.Formsendocrineandexocrinesecretoryglands.

Secretoryportion

Junquueira&Carneiro10thEd.P.82

Junqueira and Carnein 10th Ed. P. 82

EpithelialliningcellsofSkinIntestine

Multiplelayersofflat(squamous)cells Singlelayeroftall(columnar)cellsMichigan Medical School Histology Slide Collection Michigan Medical School Histology Slide Collection

Epithelialcells:1. Formavascularsheetsthatdifferinnumberofcelllayers,shapeofthecells

andstructuralspecializationsofthefree(apical)cellsurface,dependingonthetissuefunction(s).

2. Arestructurallyandfunctionallypolarized:Haveapical,lateralandbasaldomains.3. Areheldtogetherbyseveralspecializations,knownastheintercellular

junctions,andbindtotheunderlyingconnectivetissueviathebasementmembrane(LM)orbasallamina(EM).

4. Arecapableofrenewalandregeneration. non-specializedepithelium-allcells specializedepithelium-stemcells

Ross/Romrell p. 52

2. Arestructurallyandfunctionallypolarized:Haveapical,lateralandbasaldomains.3. Areheldtogetherbyseveralspecializations,knownastheintercellular

Ross/Romrell p. 52

ClassificationofEpithelium

(Pseudostratified)

columnar(Respiratory)

Ross/Romrell p. 53

PseudostratifiedEpithelium

Kierszenbaum p.6

Simplesquamousepithelium:endotheliumandmesothelium

Michigan Medical School Histology Slide School Kierszenbaum p.4

Endothelium/Mesothelium(SimpleSquamousEpithelium)

Source Undetermined

SimpleCuboidalEpithelium

Michigan Medical School Histology Slide School Kierszenbaum p.4

SimpleColumnarEpithelium

Michigan Medical School Histology Slide School Kierszenbaum p.4 Source Undetermined

Simplecolumnarepitheliumliningthegutlumen

Twolayersofsmoothmuscleon

thewallGray’s Anatomy, wikimedia commons

Michigan Medical School Histology Slide School

ApicalCellSurfaceSpecializations-1StriatedBorder(Microvilli)

G:gobletcell

Sources Undetermined

Microvilli(Coreofactinfilaments)

Darnell et al., Molecular Cell Biology p. 608

Source Undetermined

ApicalCellSurfaceSpecializations–2CiliaontheRespiratoryEpithelialCells

Kierszenbaum p.6

Verhey. Molecular Biology of the Cell, 4th Edition.

Ciliacoreofmicrotubulesin9+2arrangement(axoneme)

BasalbodiesGobletcells

RespiratoryepitheliumMichigan Medical School Histology Slide Collection Source Undetermined

9+2(Axoneme)

Dyneinisresponsibleforthesliding.

Alberts et. Al; p 648

Rossetal.,4thed.P.94

DyneinDefectsinImmotileCilia

Source Undetermined

MicrovilliandciliaMicrovilli

StratifiedSquamousEpitheliumnon-keratinizedkeratinized

Kierszenbaum pg 5 Kierszenbaum pg 5

StratifiedSquamousEpithelium

Non-keratinized Keratinized

Linesesophagus,oralcavity,vagina… Linesthickandthinskin

Michigan Medical School Histology Slide Collection Michigan Medical School Histology Slide Collection

TransitionalEpithelium(urothelium)

Kierszenbaum pg 6

TransitionalEpithelium(urothelium)

Linestheurinarytract,ureter,bladderandurethra

Source Undetermined

2. Arestructurallyandfunctionallypolarized:Haveapical,lateralandbasaldomains3. Areheldtogetherbyseveralspecializations,knownastheintercellular

Ross/Romrell p. 52

Whatstructuresholdthecellstogetherandattachesthe

epitheliumtotheconnectivetissue?

Ans.Intercellularjunctions

Basementmembrane(basallamina)

Source Undetermined

Maculaadherens(desmosomes)andIntermediateFilaments

Source Undetermined

MaculaAdherens(desmosome)

Source Undetermined

Boumphreyfr,WikimediaCommons(adapted)

Desmocollins

CellMembranes

Tonofilaments(Keratin

IntermediateFilaments)

IntercellularSpace

Adhesionplaque

(plakoglobin,desmoplakins)

Cell1 Cell2

DesmosomesandIntermediateFilamentsDesmosomesserveas:

1.Spotattachmentsitesforadjacentcellmembranes.

2.Anchoringsitesforintermediatefilaments.

Alberts et al., p. 802

Verhey. Molecular Biology of the Cell, Garland Science 2008

Basementmembrane(basallamina)

Hemidesmosomesfunctiontoanchorepithelialcellstotheconnectivetissueviabasementmembrane(basallamina).

Source Undetermined Michigan Medical School Histology Slide Collection

LossofdesmosomefunctionscauseBlisteringSkinDisorders

Pemphigus:Separationofepidermalcellsfromeachother(acantholysis)causedbylossofdesmosomefunctions.

Bullouspemphigoid:Separationofepidermisfromthedermisduetoblisteringinthebasementmembranecausedbylossofanchoringfilamentsandhemidesmosomes.

Source Undetermined

IntercellularJunctionsJunctionalComplex

Zonulaadherens(intermediatejunction)

Darnell, et. al., p.608 Lady of Hats, Wikipedia

ZonulaadherensMaculaadherens•  Intermediatejunction•  Adheringjunction•  Cadherins•  Linkedtoactinfilaments•  Adhesionbelt

•  Desmosome•  Adheringjunction•  Cadherins•  Linkedtointermediatefilaments•  Spotadheringjunction

ZonulaOccludens(TightJunction)

servesasaSelectivePermeabilityBarrier

Lady of Hats, Wikipedia

Junquueira & Carneiro 10th Ed. P. 82

Source Undetermined

Zonulaoccludens(tightjunction)

Alberts et. Al, p. 794-5

Freeze-fracturepreparation

Alberts et al., p. 795

BloomandFawcettp.67

Nexus(gapJunction)-communicatingjunction

SixConnexinsubunitsassembletoformaConnexon.

Alberts et al., p. 802 Lady of Hats, Wikipedia

GapJunction

Epithelialcells:1. Arestructurallyandfunctionallypolarized:Haveapical,lateralandbasaldomains2. Formavascularsheetsthatdifferinnumberofcelllayers,shapeofthecells

3. Areheldtogetherbyseveralspecializations,knownastheintercellularjunctions,andbindtotheunderlyingconnectivetissueviathebasementmembrane(LM)orbasallamina(EM).

Ross/Romrell p.52

EpitheliumTypes-simple&stratified(pseudostratified)ApicalcellsurfacespecializationsMicrovilli-actinfilamentsCilia-microtubules(dyneins)

IntercellularjunctionsZonulaoccludens(tightjunction)-ridgesandgrooves, sealintercellularspaces-SelectivepermeabilitybarrierZonulaadherens-actinfilaments-celltocelladhesionMaculaadherens(desmosome)-intermediatefilaments -attachmentplaque(spot)Hemidesmosome-attachesepitheliumtobasallaminaNexus(gapjunction)-connexons-celltocell communication

EpithelialcellsformSecretoryGlands

Glands:GroupingsofcellsspecializedforsecretionSecretionistheprocessbywhichsmallmoleculesaretakenupandtransformed,byintracellularbiosynthesis,intoamorecomplexproductthatisthenactivelyreleasedfromthecell.Exocrine(ducts)andendocrine(ductless)glands

SecretoryEpithelialcells

Source Undetermined

DevelopmentofEndocrineandExocrineGlands

Junquiera and Carnein, 10th Ed. P. 82

SecretoryUnitsandGlandularCells

Kim, S.K.

Image of secretory units and glandular

cells removed

TwoSecretoryPathways

Exocytosis

RegulatedSecretion:Secretorygranulesaccumulateincellsandthegranulecontentisreleasedbyexocytosisuponstimulation.

ConstitutiveSecretion:Thesecretoryproductisnotconcentratedintogranulesbutisreleasedcontinuouslyinsmallvesicles.

Kim, S.K.

LearningObjectivesAftertoday’ssession,thestudentsareexpectedto:

1. Beabletoclassifyepitheliaandidentifyeachtype.2.  Recognizefourtypesofintercellularjunctionsandhemidesmosomesattheelectronmicroscopelevelandknowtheirfunctions.

3.  Identifytheapicalspecializationsandknowtheirfunctions.

4. Beabletocorrelatedifferenttypesofepitheliatotheirfunctionsandknowwhereinthebodyeachtypeoccurs.

5. Knowhowspecializedandnon-specializedepithelialcellsarerenewed.

6. Knowhowexocrineandendocrineglandsformandbeabletorecognizesecretorycells.

AdditionalSourceInformationformoreinformationsee:http://open.umich.edu/wiki/CitationPolicy

Junqueira and Carnein 10th Ed., pg 82

Michigan Medical School Histology Slide Collection

Ross/Romrell p.52

Ross/Romrell p.53

Kierszenbaum p.6

Michigan Medical School Histology Slide Collection; Kierszenbaum p.4

Source Undetermined

Michigan Medical School Histology Slide Collection; Kierszenbaum p.4

Source Undetermined; Michigan Medical School Histology Slide Collection;

Kierszenbaum p.4

Michigan Medical School Histology Slide Collection; Gray’s Anatomy,

Wikimedia Commons, http://commons.wikimedia.org/wiki/File:Gray1056.png

Source Undetermined; Source Undetermined

Darnell et al., Molecular Cell Biology p. 608; Source Undetermined

Kierszenbaum p.6; K. Verhey

Michigan Medical School Histology Slide Collection; Source Undetermined

Rossetal.,4thed.P.94;Ross; Alberts et al., pg 648

Source Undetermined

Kierszenbaum; Kierszenbaum

Michigan Medical School Histology Slide Collection

Kierszenbaum, pg 6

Source Undetermined

Ross/Romrell p.52

Source Undetermined

Source Undetermined; CC BY Boumphreyfr,

http://commons.wikimedia.org/wiki/File:Cell_junctions.png, CC:BY-SA 3.0, http://creativecommons.org/licenses/by-sa/3.0/

Verhey. Molecular Biology of the Cell, Garland Science 2008; Alberts et al., p. 802

Michigan Medical School Histology Slide Collection; Source Undetermined

Source Undetermined

Lady of Hats, Wikipedia, http://commons.wikimedia.org/wiki/File:Adherens_Junctions_structural_proteins.svg; Darnell, et. al.,

Lady of Hats, Wikipedia, http://commons.wikimedia.org/wiki/File:Cellular_tight_junction_en.svg; Source Undetermined;

Junquueira & Carneiro 10th Ed. P. 82

Alberts et. Al, p. 794-5;

Alberts et al., p. 795; Bloom and Fawcett p. 67

Alberts et al., p. 802;

Lady of Hats, Wikipedia, http://commons.wikimedia.org/wiki/File:Gap_cell_junction_en.svg

Ross/Romrell p.52

Source Undetermined

Junquiera and Carnein, 10th Ed. P. 82

Sun-Kee Kim

09.08.08: Epithelium

Education